1. Field of the Invention
The present invention relates to an arrangement for producing structured substrates. This type of arrangement for producing structured substrates is employed in the production of integrated circuits.
2. Description of the Background Art
The typical production process for integrated circuits employs one or more photolithographic steps to define patterns on the surface of a substrate, particularly a silicon wafer. Said patterns are used in subsequent steps to provide a plurality of elements, which together form the active components and bonding circuitry of an integrated circuit.
The substrate is normally disk-shaped. A checkerboard pattern of square or rectangular chips on the substrate is formed by lines along which the chips can be separated as soon as the processing steps being performed on the substrate have ended.
Conventional photolithography comprises a number of well-known steps. In this respect, the substrate is placed in a coating device with a chuck. Then, the top substrate surface on which the circuit features are to be formed is cleaned by a liquid solvent. The solvent can include a suitable bonding agent to facilitate the adhesion of a photopolymer layer, which is applied subsequently to the substrate surface.
As the next step, the chuck is operated to rotate the substrate. This rotation throws off excess solvent until the substrate surface appears to be dry. The chuck is then turned off. After the substrate has ceased to move, a predefined amount of a photopolymer solution is applied to the substrate surface. Next, the chuck is operated to distribute the liquid photopolymer solution on the substrate surface.
As soon as the photopolymer solution has dried, it is selectively exposed to light either by using a mask or by using a direct write technique in order to structure each chip in accordance with the desired configurations of a layer of the overall layout of the integrated circuit design. Subsequent steps such as, for example, etching, doping, oxidizing, or different deposition steps are carried out with use of these and subsequently formed and patterned photopolymer layers.
Many different factors can disadvantageously influence the quality, uniformity, and reliability of the photolithographic techniques as they are used in known production processes for integrated circuits. These factors include the materials, techniques, and conditions for the application of liquid materials, particularly photopolymer solutions. Ideally, the formed photopolymer layer is of such quality that a precise photoreproduction of all microscopic details of the mask is made possible initially in the photopolymer layer, also called the photoresist layer, and then in the physical circuit elements to be formed with use of said photopolymer layer.
All physical, chemical, and environmental factors must be carefully controlled, so that none of the structuring steps with respect to a substrate or the proportions of the individual chips fail. Sometimes, individual factors alone cannot be sufficient to cause problems, but in combination they disadvantageously influence the quality particularly of the photopolymer layer and then the quality of the resulting circuit elements.
European patent EP 0 403 0 086 B1, which corresponds to U.S. Pat. No. 7,864,303, discloses an arrangement for producing structured substrates.
Known coating equipment has the problem that the different liquid materials, particularly the photopolymer solutions, are applied in such large amounts that there are considerable surpluses which cannot be used further in view of the quality.